[cmc540]

I have a 2001 540 and have been experiencing a sensation the steering is binding on hard right turns. It is especially noticeable when the car is under load like when taking an on-ramp. The wheel feels like it is locking / binding and the sensation can be heard and felt through the steering wheel. Honestly, it feels and sounds like the tire is coming into contact with the fender but it's not touching anything. It has been getting progressively worse over the past month or so. During normal driving and turns to the left, no sounds or issues.

Yesterday, I replaced the thrust arm bushings, the control arms, tie rods, center link and wheel bearings. The thrust arm bushing related issues I was having (vibration under braking) are gone. While I had everything apart, I could find no indications the tires were contacting the strut, fender or wheel well liner. Shocks show no damage or indications of leaking. Rotors and pads are fine. Back together and test drive. Everything feels good. Steering is tight, no vibration or noise. First right turn, there's the binding and the noise.

Power steering fluid is clean and at correct level. P/S hoses appear to be fine (3 have been replaced over the past 2 years). Tires have 3,000 miles on them and are still like new. No new parts, lowering or modifications to suspension that could be causing the issue or changing geometry.

In searching the issue, I found one reference to "the strut binding in its mount" as a possibility but the OP never followed up his post with the final solution to his problem. (Don't you just hate that!) I've never heard of this but has anyone here?

Before I start throwing parts at it, has anyone here got any ideas? Many thanks!

 

[herrubermensch]

This is a very common phenomenon on E39 M5's. There are plenty of posts about it. A particular cause has not been pinpointed, though most have resolved the problem by replacing either their PS pump or their steering box. For me, it ended up being a precursor to PS pump failure, so I bit the bullet and bought a new one.

Obviously, the must less drastic diagnosis is PS pump cavitation or use of regular PS fluid as opposed to synthetic ATF. Some seemed to have resolved the phenomenon by increasing the amount of ATF they run or switching to synthetic. Most by replacement of the pump, and only one that I know of by replacement of the box.

--Peter

 

[cmc540]

This is a very common phenomenon on E39 M5's. There are plenty of posts about it. A particular cause has not been pinpointed, though most have resolved the problem by replacing either their PS pump or their steering box. For me, it ended up being a precursor to PS pump failure, so I bit the bullet and bought a new one.

Obviously, the must less drastic diagnosis is PS pump cavitation or use of regular PS fluid as opposed to synthetic ATF. Some seemed to have resolved the phenomenon by increasing the amount of ATF they run or switching to synthetic. Most by replacement of the pump, and only one that I know of by replacement of the box.

--Peter

Thanks for the reply. Most of the posts that came up in my searches related to the PS pump were noise related. Were you experiencing similar feelings of the steering wheel binding? Did replacing the pump cure your problems?

Thanks again!

 

[JCM55555]

Great timing....this just started happening to me with the installation of my Super sprint Headers....I also have a slight power steering leak...

 

[herrubermensch]

Thanks for the reply. Most of the posts that came up in my searches related to the PS pump were noise related. Were you experiencing similar feelings of the steering wheel binding? Did replacing the pump cure your problems?

Thanks again!

Yes. I'm not talking about noise. I'm talking about precisely the phenomenon you described, viz., the PS all of a sudden becoming extremely heavy in tight cornering, so much so that you wonder whether you will be able to hold the turn. It feels just as you described--like the wheel is hitting the fender liner and won't go any further. In my case, it would then just as suddenly "give way" and the PS would kick back in.

As I said, I concluded that in my case, my PS pump was on the way out. I replaced it, and that issue disappeared. Another board member concluded it was his steering box. So far, I have been able to avoid that expensive replacement.

--Peter

 

[cmc540]

Peter, thanks for the additional info. After reading JCM55555's comment about the headers, I wonder if the additional underhood heat may shorten the life of the PS pump. I installed SuperSprint headers on my car last summer.

Guess I'll have to start looking for a DIY thread on PS pump replacement!

 

[herrubermensch]

Peter, thanks for the additional info. After reading JCM55555's comment about the headers, I wonder if the additional underhood heat may shorten the life of the PS pump. I installed SuperSprint headers on my car last summer.

Guess I'll have to start looking for a DIY thread on PS pump replacement!

I doubt it has anything to do with heat from the headers. Just age and use.

They are stupid simple to replace. Should take no more than an hour. Basically, drain PS fluid by removing the return hose to the PS pump and unbolting the banjo fitting. Once drained, remove the belt, remove three bolts from pulley and remove the pulley, and remove three bolts from the bracket, and voila, it's off. Reverse order for installation.

--Peter

 

[JCM55555]

Thanks Peter.

Strange that it only feels funny when turning right. Mine is most noticeable on long right hand bends entering the freeway. Taking the corner with some speed and applying a little throttle causes noticeable vibration throughout the vehicle and up through the steering wheel. If I put the clutch in and let the RPM's drop the vibration goes away even at the same steering angle and speed. Revving the engine in neutral will also trigger the vibration. My initial thought was that my cats are making contact with the heat shield (see my header thread for reference) Never happens going left...I am aware that I do have a small PS leak, but I'm not sure if I'm experiencing the same thing since it's dependent on throttle response?

 

[cmc540]

Great timing....this just started happening to me with the installation of my Super sprint Headers....I also have a slight power steering leak...

JCM55555 - I think I have finally found the answer and your post suggests you may have the same issue. I first flushed the P/S pump with new synthetic fluid. Same problem. I then replaced the P/S pump. No improvement. Had a local BMW indy check the car and he suggested I replace the steering box. Before throwing more parts at the problem, today, I had the car looked at by the BMW dealership and their mechanic found the header is slightly contacting the steering shaft and creating the binding sensation.

With a 10 year old car and old motor mounts, I would welcome opinions on whether or not new motor mounts might lift the motor the slight amount necessary to eliminate the contact between header and steering shaft. I guess the other solution would be to "dimple" the header to create additional clearance.

I really feel stupid that I wasted money on the P/S pump that apparently wasn't needed. I sure am glad I didn't go for the steering box replacement!

Any thoughts or suggestions would be appreciated.

Thanks,

Chris

 

[JCM55555]

JCM55555 - I think I have finally found the answer and your post suggests you may have the same issue. I first flushed the P/S pump with new synthetic fluid. Same problem. I then replaced the P/S pump. No improvement. Had a local BMW indy check the car and he suggested I replace the steering box. Before throwing more parts at the problem, today, I had the car looked at by the BMW dealership and their mechanic found the header is slightly contacting the steering shaft and creating the binding sensation.

With a 10 year old car and old motor mounts, I would welcome opinions on whether or not new motor mounts might lift the motor the slight amount necessary to eliminate the contact between header and steering shaft. I guess the other solution would be to "dimple" the header to create additional clearance.

I really feel stupid that I wasted money on the P/S pump that apparently wasn't needed. I sure am glad I didn't go for the steering box replacement!

Any thoughts or suggestions would be appreciated.

Thanks,

Chris

Thanks for the follow up Chris. I've had my car up on a lift since my last post and confirmed that the headers are not contacting the steering shaft but rather are only making contact with the heat shield on the sub frame. I have new connecting pipes that will solve the problem but have not had time to have them installed yet.

 

[E55AMG2]

My M5 did this....it was indeed a failing PS pump. I replaced it, and problem went away. If you replace the PS pump and it still persists, you likely have a steering box issue.

 

[cmc540]

Success at last!

Last update to wrap this up. Installed new motor mounts. Left side mount was broken. Almost fell into two parts when removed. New mounts has solved the problem. Header now has clearance. No more binding or noise on turns! Life is good!!

Wish I hadn't replaced a perfectly good power steering pump. Doubly glad I didn't replace the steering box!!

Cheers!

Chris

 

[Vector57]

Last update to wrap this up. Installed new motor mounts. Left side mount was broken. Almost fell into two
parts when removed. New mounts has solved the problem. Header now has clearance. No more
binding or noise on turns! Life is good!!

Wish I hadn't replaced a perfectly good power steering pump. Doubly glad I didn't replace the steering box!!

Cheers!

Chris

Well done! Glad to hear you got it ironed out.

Thank you for reporting back with your findings.

Regards,
Alan

 

[nixter]

I'm having this issue. No noise just binding on slow or stationary right turns of the wheel. I replaced the pump in February due to vibration felt through the pedals and steering wheel along with a hissing noise. Now I'm wondering if the core problem was the box all along. I'm feeling very subtle vibration in the pedals and wheel again so perhaps my steering box is killing my pumps? I had a mechanic look today and while he didnt have a ton of time he thought is was likely the box. :/

The header thing... would that only be with after market headers?